- Accelerated Cost Recovery System (ACRS)
- Accelerated Depreciation
- Accountable Plan
- Accounting Method
- Accounting Period
- Accrual Method of Accounting
- Accrued Interest
- Acquisition Debt
- Active Participant
- Active Participation
- Actual Expenses (Regular Method)
- Additional Child Tax Credit
- Adjusted Basis
- Adjusted Gross Income (AGI)
- Adjustment to Income
- Adoption Credit
- Advance Earned Income Credit
- Advance Payments
- Alimony Payments
- Alternative Minimum Tax (AMT)
- Amended Return
- Amortization
- Amount Realized
- Annualized Income
- Annuitant
- Annuity
- Annuity Starting Date
- Anti-Churning Rules
- Asset
- At-Risk Rules
- Audit
- Automobile Expenses
- Average Basis
- Away From Home Overnight